The present invention relates to a device for controlling a railroad track making or repairing machine, which comprises on the one hand a laser emitter mounted on a skip standing on the track or the lay-out thereof ahead of the machine, and adapted to emit a first fan-shaped or sweeping beam in a horizontal plane and a second fan-shaped or sweeping beam in a vertical plane, and on the other hand a laser receiving unit mounted on the machine and comprising a first receiver for the horizontal beam and a second receiver for the vertical beam, both receivers being designed for automatic adjustment as a function of the impact line of one or the other of said laser beams at positions corresponding to the desired positions of the working members of the machine.
Relative-base measuring units have already been used for performing track levelling and lining works, and mounted notably on tamper-leveller-liners.
A known feature of relative-base measuring units of this type is that they reduce appreciably track defects in both horizontal and vertical planes as a function of their geometry in a proportion ranging from 1:3 to 1:4. Another feature inherent to those units is their capacity of reducing the geometric defects of railroad tracks when their wavelengths are less than 20 m. On the other hand, to correct track defects when the wavelength is above 20 m. the use of a longer measurement base consisting either of an optical system or of a laser system becomes necessary.
Existing laser systems comprise emitters generating fan-shaped or sweeping beams either horizontally for levelling operations or vertically for shifting operations. Laser emitters equipped with special optical systems generate horizontal and vertical beams either on the same axis or shifted parallel thereto by means of mirrors. However, this arrangement is objectionable in that one fraction of the laser power out-put is lost in the optical system at the expense of precision and of a reduction in the actual working length. Superposed beams can only be used for alignment purposes since the curves of the two receivers do not follow the same path. Besides, if two separate laser emitters are used, the vertical beam (for shifting or lining) will inevitably intersect at one time the working field of the horizontal beam for the levelling function, thus rendering the complete system inoperative.